"You'll want your camera out for this," Dierig said as he lifted up the lid to a cryogenic freezer capsule. In the cryo chamber, the collection expands to include not just seeds, but animal embryos, semen and microbes.

Grace HoodKUNC

When unapproved genetically modified wheat was found growing in Oregon earlier this year, it didn't take long for accusations to start flying. A flurry of initial finger-pointing cast potential blame on a federal seed vault in Fort Collins, Colo., which housed the same strain of wheat, developed by Monsanto Corp., for about seven years up until late 2011.

The facility has been cleared of wrongdoing since then. A U.S. Department of Agriculture spokesman says all of Monsanto's 1,500 pounds of wheat seeds held at the vault were incinerated a year and a half ago at the corporation's request. But the investigation raises the question of how secure these seed vaults actually are.

There are no high, barbed-wired fences. No barking Dobermans. No armed guards. Just a friendly welcome video playing in the lobby and a warm-natured receptionist behind a desk, who hands you a clipboard with a sign-in sheet.

But that doesn't mean the center is lax on security. From the outside it may not look like a bastion of the American agriculture industry. Inside, it holds one of the world's largest collections of seeds, genetic material for livestock, microbes and endangered plants under highly sophisticated lock and key.

Upstairs in the facility's main cold storage vault, ceiling-high shelves hold seemingly endless rows of white pouches. In this room, there are 600,000 seed packets, which puts the total number of seeds in the billions. The temperature is kept at a level similar to a home freezer, at low humidity to arrest seed degradation and keep them viable longer.

"They're all bar-coded so we know exactly where everything is," said Dave Dierig, research leader at the center and one of six people in the building with access to the vaults. Another security measure is the labeling system. Looking at a seed pouch, there's nothing that tells you what kind of seeds you're holding, just a bar code. You need access to a secure database to find out what's inside.

To the right of the large, gray metal vault doors, a TV screen shows a live stream of the seed vault. It serves as another reminder of the building's emphasis on security. In this place, you're always on camera.

Other seed vaults throughout the world store their back-up collections here because of the facility's reputation not just for the promise of security but also the ability to preserve the viability of seeds for longer periods of time. Private companies such as Monsanto and Dupont can also store their seeds in the federally owned building.

"It would really be a rare case where we would keep another company's seed. There'd have to be some kind of extenuating circumstances, for them to say, 'We need you to keep this seed,' " Dierig said.

Even though it is rare, privately owned, genetically modified seed does make it into storage. That's how all eyes fell on the vault's doors when news broke in June about Monsanto's glyphosate-resistant wheat, commonly called Roundup Ready, found growing in small volunteer patches in a field in Oregon.

There's a building at Colorado State University that houses what amounts to a big insurance policy, in case there's a loss of plant or animal life on a regional or even global scale. Behind the vault at this federal facility: billions of seeds and also a lot of genetic material. As you can imagine, the place has high security. And it was also recently under investigation as a possible source of genetically-modified wheat, that was found mysteriously and illegally growing in Oregon.

Luke Runyon, from member station KUNC, begins by taking us into the vault.

LUKE RUNYON, BYLINE: I'm standing here in front of the National Center for Genetic Resources Preservation, which is just a fancy way of saying seed vault. It's beige with a red roof, three stories tall. But it's the nation's largest collection of seeds, genetic material for livestock and microbes. So let's go inside see what's going on.

(SOUNDBITE OF A GATE CLOSING)

RUNYON: Inside the facility, good luck getting past the lobby without a key card and pass code. Locked doors are around every corner. Luckily, I have a tour guide.

RUNYON: Dierig is in charge of the seed vault. The facility has been compared to Fort Knox in its level of security. This one building serves as the back-up seed collection for about 30 other vaults around the country and dozens from around the world.

DIERIG: So yeah, these are the doors to the vault. And these are opened and closed every day.

(SOUNDBITE OF BEEPING)

RUNYON: We're about to head into the facility's black box storage room. Think of it like a series of safety deposit boxes in a bank. Only it's kept at the same temperature as your home freezer. Fur-lined parkas hang on a rack just outside the large grey metal doors.

DIERIG: You may want to put on a jacket, but it actually feels kind of good now that it's summer time.

RUNYON: To the right of the doors, a TV screen shows a live stream of the seed vault. It serves as another reminder of the building's security. In this place, you're always on camera.

(SOUNDBITE OF A GATE CLOSING)

DIERIG: Deep breath.

RUNYON: Hoo.

DIERIG: We won't stay in here too long.

RUNYON: Inside, ceiling-high shelves hold 600,000 seed packets, which puts the total number of seeds in the billions.

ANGELA SOSA: We have anything from fish to cattle to sheep. We even do some cattle blood. So pretty much that's what we do so we can put it in our big database and it's accessible - and we know where it is.

RUNYON: Lab technician Angela Sosa is transferring Chinook salmon eggs from one container to another, placing them into the liquid nitrogen.

This facility also serves as a back-up for some private ag companies like DuPont and Monsanto. And this spring, the building's formidable reputation was thrown into question. For seven years, this same vault kept about 1500 pounds of Monsanto's genetically modified wheat seeds, including the same strain found growing in Oregon. Dierig says because of the vault's security, it's often called on to play an impartial role in contentious court battles over genetically modified seeds.

DIERIG: The court may say deposit it in some kind of neutral location, and keep it there until we decide what's going to happen with it.

RUNYON: Dierig says he can't comment on the specifics of the Oregon case, as Department of Agriculture investigators are still trying to pin down the seeds' source. Seed vault staff incinerated the stash of GMO wheat seeds two years ago. With the investigation turning in other directions, this beige building in Colorado can return to business as usual, securely storing the world's seeds.

For NPR News, I'm Luke Runyon in Fort Collins, Colorado.

GREENE: And Luke's story came to us from Harvest Public Media, a Public Radio collaboration that focuses on agricultural issues. Transcript provided by NPR, Copyright NPR.